System and User Language

there are two things:
-there is languagesetup, which will run at a normal install, and I guess it saves its data in /Library/Preferences/.GolbalPreferences.plist. (or in the Library folder of the root user, as written on macenterprise link below) AutoDMG does not run this tool, so this file is not there, so english is default.

I think you can do two things: edit these files, or make a script to run languagesetup again.

See these links, I think they will solve your issue (if I understand you correctly)
macenterprise group read the post from Rolf Kocherhans on 28-10-14:

Hello all problem solved ! It has nothing to do with AutoDMG or some other imaging procedure, Apple must have changed something in the way they make the images. The default values (for language and keyboard layout) are stored in the .GlobalPreferences plist of the root user ! The solution is: 1. make the vanilla created by AutoDMG or any other procedure writable 2. execute this two default writes sudo defaults write /Volumes/Macintosh HD/var/root/Library/Preferences/.GlobalPreferences AppleLanguages "(de, en)" sudo defaults write /Volumes/Macintosh HD/var/root/Library/Preferences/.GlobalPreferences AppleLocale -string de_CH 3. make the vanilla read only compressed again 4. renew the checksum (asr imagescan) done !

examples how to use languagesetup from krypted

Hello - I solved the same Problem with mojave.

1. Copy "Install macOS Mojave.app" to a new folder
2. Make an image from previous folder
3. Mount the DMG
4. Start AutoDMG and drop the installer fom the DMG to it

Step 1-4 is because of a bug in macOS installer

1. Mount the image read/write with the shadow option hdiutil attach osx-10.14-18A391.apfs.dmg -shadow osx.shadow Mountpoint is "/Volumes/Macintosh HD 1" Make necessary changes

2. modify "/Volumes/Macintosh HD 1/private/var/root/Library/Preferences/.GlobalPreferences.plist"
   NOT with "defaults write" but with vo or another editor because its an XML File
   Here's my file:

   <?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
   <plist version="1.0">
   <dict> <key>AppleKeyboardUIMode</key> <integer>3</integer> <key>AppleLocale</key> <string>de_DE</string>
   </dict>
   </plist>

3. Modify /Library/Preferences/.GlobalPreferences.plist
   defaults write "/Volumes/Macintosh HD 1/Library/Preferences/.GlobalPreferences.plist" AppleLanguages "(de, en)"

4. Convert the DMG back to read only embedding the changes from the shadow file. hdiutil convert osx-10.14-18A391.apfs.dmg -format UDRW -o new.dmg -shadow osx.shadow
5. Create the VM using vfuse (I use a teplate to crate it). vfuse -t vfuse-template10-14.json Here's my template: { "source_dmg": "/Users/user/Jamf/Jamf/new.dmg", "output_dir": "/Users/user/Jamf/vms", "output_name": "macos-10-14-jamf", "cache": false, "hw_version": 12, "mem_size": 4096, "disk_type": 0, "bridged": false, "mac_address": "", "enable3d": true, "vnc_port": 5901, "vnc_passwd": "", "hw_model": "MacBookAir7,2", "serial_number": "XXXXXXXXXXXX", "snapshot": true, "snapshot_name": "base-snapshot", "shared_folder": "/Users/user/Documents", "packer_template": "" }
6. macOS Installer comes in german.

I have used previously in a setup script:

#!/bin/bash
defaults write /Library/Preferences/.GlobalPreferences.plist AppleLocale "en_NZ"
defaults write /Library/Preferences/.GlobalPreferences.plist Country "NZ"

No idea if it still works as I went to a deployment only model a couple of years ago, but unless Apple has changed something it should, adjust language and country to suit (they do have to match exactly as required so you may need to query a correct machine).